This invention generally relates to merchandise security systems.
Merchandise security systems are increasingly in demand due to the high cost of small and portable items such as tape players, video cameras and laptop computers, and the ease by which these items can be stolen from retailers. The majority of security systems protect items on display by adhering some form of sensor to the displayed items. Conventionally, a sensor is a simple switch having a protruding member which is depressed when the sensor is mounted onto the protected item, thus closing the switch. When a theft is attempted, the sensor is detached from the item thus opening the switch and causing an alarm to sound.
Some security systems connect sensors directly to a central unit while others group multiple sensors together for one location in a store and connect the grouped sensors to a local control box or a hub. For security systems having hubs, the sensors are wired to the hub using the hub cables through a jack. Each hub can accommodate multiple sensors. However, if less than the full capacity of sensors are connected to a particular hub, all unused sensor jack locations must be shunted via shunting plugs which emulate closed sensor switches.
The various hubs are connected to a central unit. When a sensor is activated, an alarm event is generated. The alarm event is detected by the control unit which causes the alarm to sound. When the alarm sounds, on some systems, a sensor indicator close to the sensor jack turns ON to indicate which sensor caused the alarm. After the alarm sounds, depressing the protruding member of the sensor generating the alarm event stops the sensor from generating further alarm events and turns the sensor indicator OFF, but the alarm is not stopped. The alarm can only be stopped by resetting the control unit.
Most conventional sensors utilize a switch which closes a sense loop when the sensor is attached to any flat surface. When the sensor is removed, the switch is opened, and the sense loop is opened causing an alarm event. This kind of sense loop scheme is susceptible to false alarms. A false alarm can occur, for example, when the plug connecting the sensor to the jack on the hub is temporarily misaligned causing the sensor to be temporarily disconnected from the hub. This disconnection opens the sense loop and is detected as an alarm event causing the control unit to set off the alarm, even though no theft is being attempted. In addition, the sensor indicator turns ON only when the sense loop is open. Accordingly, the sensor indicator turns ON and OFF intermittently for this kind of temporary disconnection. When the temporary misalignment recovers, the sensor indicator, if offered, turns OFF and all indications of the location of the misalignment are lost.
When a sensor is removed from a protected item, the sensor generates an alarm event because the sensor switch is open. A store attendant normally responds by disarming the alarm so that customers are not disturbed by the annoying alarm sound and notes the location of the sensor that caused the alarm as indicated by the sensor indicator, if offered. Then, the attendant determines whether the merchandise protected by the activated sensor has been stolen, or the sensor was compromised in some other manner. The store attendant corrects the alarm event condition by properly remounting the sensor onto the merchandise or disconnecting the sensor from the control unit if the sensor is damaged or defective. Only when the alarm event condition is corrected, can the security system be rearmed.
The above scenario is complicated by the occurrence of false alarms, such as misaligned jacks or improperly mounted sensors. When a false alarm of the intermittent variety occurs, the security system alarm is triggered. The store attendant goes through the normal steps attempting to locate and correct the cause of the alarm. However, since the cause of the alarm was only momentary, by the time the attendant reaches the control unit, the cause of the alarm has vanished and the sensor indicator, if offered, is OFF. Thus, the attendant is unable to identify the cause of the alarm. Since the alarm event no longer exists, the store attendant typically attempts to reset the control unit and if the system rearms, the store attendant assumes that only a false alarm had occurred.
This intermittent false alarm problem is exploited by shoplifters. The shoplifter first sets off the security system alarm by disconnecting a sensor from an article of merchandise. Then, after the alarm has sounded, the sensor is remounted onto the merchandise. When the store attendant checks for the location of the sensor causing the alarm, all the sensor indicators, if offered, are OFF. The store attendant assumes that the alarm was an intermittent false alarm and resets the control unit. Since the sensor was replaced by the shoplifter, alarm events are no longer generated and the security system alarm remains quiet.
Then, the shoplifter disconnects another sensor, causing a second alarm to sound, and again remounts the sensor back onto the merchandise. The store attendant again checks for the sensor that caused the alarm and, finding none, resets the control unit again thinking that another intermittent false alarm has occurred. This scenario is repeated several times until the store attendant simply assumes that the security system is too annoying to deal with, and turns the entire security system OFF. At this point, the shoplifter can steal any unprotected item from the previously protected and displayed items.
Further, a sensor plug can be removed from a hub and replaced by a shunting plug instead. The alarm will sound, even though none of the sensors have been removed from the protected merchandise. Since shunting plugs are normally used to shunt out unused jack locations, an attendant can easily overlook the additional shunting plug and rearm the control unit with the shunting plug replacing a sensor plug. The shoplifter is then free to remove the item previously protected by the now disconnected sensor.